App is crashing after trying to free reassigned pointer

This is the place where crash happens, if you remove this line then there will be no crash. And if this pointer is not freed then it leads to a huge memory leak
```Dart
// CRASH IS HAPPENING HERE:
calloc.free(buffer);
```

```yaml
ffi: ^2.1.0
win32: ^5.0.7
```
```Dart
import 'dart:ffi';

import 'package:ffi/ffi.dart';
import 'package:flutter/material.dart';
import 'package:win32/win32.dart';

/// Loops through all system processes with [NtQuerySystemInformation].
Future loopThroughSystemProcessesWithNtApi(Function callback) async {
final Pointer dwSize = calloc();
Pointer buffer = calloc();

// SystemProcessInformation = 5;
int info = dNtQuerySystemInformation(5, nullptr, 0, dwSize);

// [STATUS_INFO_LENGTH_MISMATCH] means that we've got the size and now need
// to call this method once again but with actual pointer to the buffer
if (!ntSuccess(info) && info == statusInfoLengthMismatch) {
calloc.free(buffer);
buffer = calloc(dwSize.value);
info = dNtQuerySystemInformation(5, buffer, dwSize.value, dwSize);
}

// Failed to retrieve processes list
if (!ntSuccess(info)) {
calloc.free(dwSize);
calloc.free(buffer);
return false;
}

// Loop through all found entities
while (buffer.ref.nextEntryOffset != 0) {
try {
// Stop looping if we found what we've been looking for
final bool result = await callback.call(buffer) as bool;
if (result) break;

// Stop updating the loop to avoid crashes
if (buffer.ref.nextEntryOffset == 0) break;

// Update buffer to the next process
buffer = buffer
.cast()
.elementAt(buffer.ref.nextEntryOffset)
.cast();
} catch (_) {
break;
}
}

// CRASH IS HAPPENING HERE:
calloc.free(buffer);

calloc.free(dwSize);
return true;
}

/// Macros for NTSTATUS.
const int statusInfoLengthMismatch = -1073741820;

// Shortcut for Pointer
typedef PULONG = Pointer;

/// Checks if Nt... function has succeded.
bool ntSuccess(int result) => result >= 0;

// Allocalte ntdll API
final Pointer _ntdllTitle = 'ntdll.dll'.toNativeUtf16();
final int _ntdllHndle = GetModuleHandle(_ntdllTitle);

/// Dart representation of native [NtQuerySystemInformation] function.
/// ```c
/// [in] SYSTEM_INFORMATION_CLASS SystemInformationClass,
/// [in, out] PVOID SystemInformation,
/// [in] ULONG SystemInformationLength,
/// [out, optional] PULONG ReturnLength
/// ```
int Function(int, Pointer, int, PULONG)?
_pNtQuerySystemInformationFunc;

/// [NtQuerySystemInformation may be altered or unavailable in future versions
/// of Windows. Applications should use the alternate functions
/// listed in this topic.] Retrieves the specified system information.
int dNtQuerySystemInformation(
int dwFlag,
Pointer buffer,
int dwSize,
PULONG out,
) {
if (_pNtQuerySystemInformationFunc == null) {
// Find function address with
final Pointer ansi = 'NtQuerySystemInformation'.toANSI();
final Pointer pNtQuerySystemInformation = GetProcAddress(_ntdllHndle, ansi);
calloc.free(ansi);

// Return 0 if function was not found
if (pNtQuerySystemInformation == nullptr) return 0;

_pNtQuerySystemInformationFunc = pNtQuerySystemInformation
.cast>()
.asFunction();
}

return _pNtQuerySystemInformationFunc?.call(dwFlag, buffer, dwSize, out) ?? 0;
}

/// Basic info about the process
sealed class SystemProcessInformation extends Struct {
@Uint32()
external int nextEntryOffset;
@Uint32()
external int numberOfThreads;
external LargeInteger workingSetPrivateSize;
@Uint32()
external int hardFaultCount;
@Uint32()
external int numberOfThreadsHighWatermark;
@Uint64()
external int cycleTime;
external LargeInteger createTime;
external LargeInteger userTime;
external LargeInteger kernelTime;
external UnicodeString imageName;
@Int32()
external int basePriority;
@IntPtr()
external int uniqueProcessId;
@IntPtr()
external int inheritedFromUniqueProcessId;
@Uint32()
external int handleCount;
@Uint32()
external int sessionId;
@IntPtr()
external int uniqueProcessKey;
@IntPtr()
external int peakVirtualSize;
@IntPtr()
external int virtualSize;
@Uint32()
external int pageFaultCount;
@IntPtr()
external int peakWorkingSetSize;
@IntPtr()
external int workingSetSize;
@IntPtr()
external int quotaPeakPagedPoolUsage;
@IntPtr()
external int quotaPagedPoolUsage;
@IntPtr()
external int quotaPeakNonPagedPoolUsage;
@IntPtr()
external int quotaNonPagedPoolUsage;
@IntPtr()
external int pagefileUsage;
@IntPtr()
external int peakPagefileUsage;
@IntPtr()
external int ppivatePageCount;
external LargeInteger readOperationCount;
external LargeInteger writeOperationCount;
external LargeInteger otherOperationCount;
external LargeInteger readTransferCount;
external LargeInteger writeTransferCount;
external LargeInteger otherTransferCount;
@Array(1)
external Array threads;
}

/// Represents a 64-bit signed integer value.
sealed class LargeInteger extends Union {
external _LargeIntegerFirst firstStruct;
external _LargeIntegerSecond secondStruct;
@Int64()
external int quadPart;
}

/// Structure for LargeInteger union.
sealed class _LargeIntegerFirst extends Struct {
@Uint32()
external int lowPart;
@Int32()
external int highPart;
}

/// Structure for LargeInteger union.
sealed class _LargeIntegerSecond extends Struct {
@Uint32()
external int lowPart;
@Int32()
external int highPart;
}

/// The SYSTEM_THREAD_INFORMATION structure contains information about
/// a thread running on a system.
sealed class SystemThreadInformation extends Struct {
external LargeInteger kernelTime;
external LargeInteger userTime;
external LargeInteger createTime;
@Uint32()
external int waitTime;
external Pointer startAddress;
external ClientID clientId;
@Int32()
external int priority;
@Int32()
external int basePriority;
@Uint32()
external int contextSwitches;
@Uint32()
external int threadState;
@Uint32()
external int waitReason;
}

/// The UNICODE_STRING structure is used to define Unicode strings.
sealed class ClientID extends Struct {
@IntPtr()
external int uniqueProcess;
@IntPtr()
external int uniqueThread;
}

/// The UNICODE_STRING structure is used to define Unicode strings.
sealed class UnicodeString extends Struct {
@Uint16()
external int length;
@Uint16()
external int maximumLength;
external Pointer buffer;
}

void main() {
loopThroughSystemProcessesWithNtApi(
(Pointer info) {
print('123');
return false;
},
);
runApp(const MyApp());
}

class MyApp extends StatelessWidget {
const MyApp({super.key});

// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// TRY THIS: Try running your application with "flutter run". You'll see
// the application has a blue toolbar. Then, without quitting the app,
// try changing the seedColor in the colorScheme below to Colors.green
// and then invoke "hot reload" (save your changes or press the "hot
// reload" button in a Flutter-supported IDE, or press "r" if you used
// the command line to start the app).
//
// Notice that the counter didn't reset back to zero; the application
// state is not lost during the reload. To reset the state, use hot
// restart instead.
//
// This works for code too, not just values: Most code changes can be
// tested with just a hot reload.
colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
useMaterial3: true,
),
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}

class MyHomePage extends StatefulWidget {
const MyHomePage({super.key, required this.title});

// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.

// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".

final String title;

@override
State createState() => _MyHomePageState();
}

class _MyHomePageState extends State {
int _counter = 0;

void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}

@override
Widget build(BuildContext context) {
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// TRY THIS: Try changing the color here to a specific color (to
// Colors.amber, perhaps?) and trigger a hot reload to see the AppBar
// change color while the other colors stay the same.
backgroundColor: Theme.of(context).colorScheme.inversePrimary,
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
//
// TRY THIS: Invoke "debug painting" (choose the "Toggle Debug Paint"
// action in the IDE, or press "p" in the console), to see the
// wireframe for each widget.
mainAxisAlignment: MainAxisAlignment.center,
children: [
const Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headlineMedium,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
```